Generally, the use of tungsten carbide (WC) or cobalt (Co) alloys as materials for the cutting inserts of cutting tools employed in the mining industry is limited by physical properties of the tool per se as well as by relatively low resistance of the WC—Co-based cutting inserts to impacts and flexural loads. Moreover, in Europe WC and Co alloys are regarded as carcinogenic materials unsuitable for production and use. In many cases, the use of tool materials strengthened by reinforcing coatings depends on operating conditions. For example, in the mining industry, coating-reinforced cutting tool inserts cannot be efficiently used because the need for frequent change of such inserts significantly decreases efficiency of the cutting process and mining and impair operating conditions for workers. For the last 70 years, cutting tools have been equipped with cutting inserts made predominantly from WC—Co alloys, which have low resistance to dynamic loads and are ecologically hazardous.
On the other hand, the performance characteristics and operating conditions of cutting tool inserts may to a great extent depend on the type of the material and the condition of the cutting-tool holders into which the cutting inserts are incorporated. For example, there is a great difference in wear-resistant properties between the material of a cutting-insert holder and the material of a cutting-tool insert because the material of the insert is “washed out” from the steel holder. This, in turn, increases the protruding length of the insert and, eventually, leads to insert breakage under the effect of flexural loads and impacts.
Furthermore, the rapid cooling of cutting tools for the purpose of creating better operating conditions and for increasing cutting efficiency develops a network of cracks in the material of the hard alloy. These cracks lead to cutting-tool breakage and to an increase in dynamic load on the equipment. Contact with products of cutting-chip breakage is hazardous to the health of working personnel and therefore demands additional safety measures. All of this further contributes to the increase in final production.
Physical and mechanical properties of known tool materials limit the design possibilities for development of new design tools and for saving energy consumed by cutting and mining processes.
U.S. Pat. No. 5,382,116 issued in 1995 to Nakanishi discloses a ground-reforming method with a hardening material mixed and injected at super-high pressure. The method provides strengthening of the metal by subjecting it to intensive cooling under high pressure. This method, however, is not suitable for strengthening tool steel by converting it into a massive homogenously strengthened composite material (hereinafter referred as “massive composite material”) and therefore does not allow use of all advantages inherent in composite materials of high strength.
U.S. Patent Application Publication No. 20070084263 published in 2007 (inventor: Zurecki) discloses changes in the material of a billet by impinging the material with a jet of a cryogenic liquid. Such treatment efficiently cools the surface of the material and provides hardening. However, the method does not ensure deep penetration of the jet into the body of the ingot and therefore is not suitable for production of a massive composite material for use in tool manufacturing.
U.S. Patent Application Publication No. 20040164058 published in 2004 (inventors: Sanders, et al) describes a method for changing the material structure by acting onto the surface of the material with a steam of solid particles. In accordance with the method, a molten material is applied to the surface of the tool through a nozzle. Use of electrical energy to melt the material and to accelerate the stream modifies the surface of the material being treated. However, in spite of the high level of energy of the stream, the method does not cause changes in the entire volume of the steel billet and cannot be used to produce massive composite materials suitable for the tool-manufacturing industry.
U.S. Pat. No. 4,295,896 issued to Flemings, et al, in 1981 discloses metal compositions having significantly improved mechanical properties and substantially free of second-phase material. The method does allow production of massive composite materials under static conditions. The original material that represents a multiphase system is heated to a temperature higher than the unbalanced temperature of the Solidus curve, and the liquid-solid mixture is subjected to high pressure that extrudes the liquid through the filter. Simultaneously, high pressure is applied to the solid body to keep the diluted materials in a solid state and to provide for preservation of the secondary phase of the material. After removal of the inter-dendrite liquid, the steel structure is preserved by means of rapid cooling of the alloy. However, this is an energy-consuming process resulting in low productivity. The structure of the composite produced according to the above method does impart improve dynamic properties to the obtained material.
A method for processing the surface of a polymeric item by impact penetration (implantation) of macro particles to improve strength, friction resistance, and other surface properties is described in U.S. Pat. No. 5,330,790 issued to Calkins in 1994. High-pressure treatment with a slurry of a liquid mixed with a ceramic particulate material ranging in size from 66 to 350 μm can be employed to implant the strengthening particles into the surface of a polymeric article. Similarly, impact implantation with electrically conductive or magnetic materials can be employed to attain a conductive surface or a surface having electromagnetic radiation absorption characteristics. In addition to water-jet impact implantation, also disclosed are methods of ultrasonic, sheet explosive, and mechanical particle implantation. Ceramic macro particle for implantation was selected from the group consisting of electro-corundum (Al2O3), boron-carbide (BC), silicone-carbide (SiC), titanium di-boride (TiB2), boron nitride (BN), quartz (SiO2), garnet, zirconium, or a mixture of the above. However, the above method is applicable for strengthening the surface of plastics only. Strengthening of a steel body by implanting a mixture of liquids, gas, and solid particles is not possible in the manner described in the patent. The effect of the high-pressure stream, as suggested in the method, does not result in super-deep penetration. Therefore, such a method is not suitable for producing massive steel composite materials.
USSR Inventor's Certificate No. 800235 published in 1981 (inventors: S. Usherenko, et al) in Bulletin No. 4 discloses a complex process of manufacturing a cutting tool, including heat treatment, mechanical treatment, protection of areas that are not subjected to cementation, and gaseous cementation of remaining areas. Prior to cementation, the parts are spatially alloyed by a jet of powdered aluminum oxide with jet velocity ranging from 1.1 to 90 km/sec under pressure of 105 to 108 kg/cm2. This method allows spatial rearrangement of the steel structure under conditions of super-deep penetration of the alloying material and produces a massive composite tool material. However, the method disclosed in the aforementioned Inventor's Certificate provides neither noticeable improvement in physical and mechanical properties of tool material such as high-speed steel nor uniformity of property changes over the length of the treated item.
Known also is a method of manufacturing an instrument disclosed in USSR Inventor's Certificate No. 703585 published in 1979 in Bulletin No. 46 (Inventor: C. Usherenko, et al). The method comprises volumetric strengthening of a cutting-tool insert with a high-speed jet of an alloying element, cleaning of the insert on the jet-introduction side for removal of micro-craters, soldering of the insert to the insert holder, sharpening of the cutting edges, and heat treatment. The process makes it possible to produce a mining cutting tool with a cutting insert from a composite tool material. However, the process does not provide uniformity of properties over the length of the cutting insert. Furthermore, heat treatment of the cutting tool in an assembled state (after soldering) decreases hardness of the holder material and thus shortens the tool service life because of low resistance of the holder to flexural deformations that occur under impact loads.
Another method described by U. A. Glasmacher et al, in Physical Review Letters, 96, 195701 (17 May 2006) relates to conversion of a solid-body structure into a composite material due to formation of local amorphous zones in the volume of graphite and zirconium. To achieve this effect, a solid body is irradiated with a flow of high-energy ions while being maintained under high pressure. However, manufacturing of composite materials by the method described in the above publication involves use of complex and expensive large-scale equipment that consumes a lot of energy and is not very productive.
Another method suitable for manufacturing a massive composite tool material is disclosed by O. Figovsky and S. Usherenko in Nanocomposite Tool Steels—Proc. Composites, Nano Engineering (ICCE 15), Haikou, Hainan Island, China, Hi. of the Orient, 15-21 Jul. 2007, p. 227-228. The article describes a method for manufacturing a nanocomposite that involves pulsed treatment of a steel blank in a mode of super-deep volumetric penetration and passage clusters jets of working medium) of ceramic microparticles (Al2O3) into and through the reinforcing structure of high-speed steel to the depth of 0.1 to 0.2 m. In up to 30% of the deeply penetrated volume, the particles form transverse reinforcing areas under conditions of accumulated energy (pressure), intense deformation, radiation flow of high-energy ions, and specific interaction of the introduced substance with the steel matrix in narrow and deep zones, with formation of fibrous metastable compounds in less than 1% of the volume and formation of areas having strong mechanical properties in up to 10% of the volume, i.e., without substantial change in the structural and physical characteristics of the original material. Final strengthening of the processed material is achieved after a final heat treatment. Nevertheless, the method described above still does not provide a composite tool material with mechanical properties of a sufficiently high level and uniformity over the depth.